Electric snap key switch assembly



Feb. 25, 1969 LANGENBERGER ET AL 3,430,012

ELECTRIC SNAP KEY SWITCH ASSEMBLY Filed Dec. 12, 1966 Sheet of 2 Feb.25, 1969 H LANGENBERGER ET AL 3,430,012

ELECTRIC SNAP KEY SWITCH ASSEMBLY Filed Dec. 12. 1966 Sheet 2 of 2 Fig.4

IN VE N TOR:

f [ma may United States Patent W 40,597 US. Cl. 20067 Int. Cl. H01h21/04 5 Claims ABSTRACT OF THE DISCLOSURE A spring switch key assemblyfor the keyboard of an electric calculating machine having a key shaftslidably mounted in an elongated housing. Contacts are disposed in thebottom of the housing. A snap spring mechanism is arranged to engage acontact arm with the contacts. An angular lever is pivotally mounted inthe housing and connected to the lever and mechanism wherein depressionof the key closes a circuit and the return of the key to its normalposition closes a second circuit. In addition, there are cooperatingnotches and ribs on the switch key housing and keyboard opening formounting of the housing in the keyboard.

The keyboard of an electric calculating machine contains a plurality ofkeys for the introduction of data into the calculating machine. Suchkeys are generally in the form of switches and each key comprises ahousing having a contact therein connected to a source of electricalenergy with the contact being engaged to complete the circuit when thekey is depressed.

Numerous types of switch keys have been devised for introducing datainto electric calculating machines upon the depression of the key. Suchkeys are generally spring switches or snap switches which, upon thedepression of the key, will move a resilient switch contact intoengagement with a stationary contact to close a circuit with the circuitbeing broken when the key is lifted or otherwise returned to its normalposition. A major disadvantage of this type of a switch key is that itis difficult for the operator to ascertain with certainty whether or notthe data which was supposed to have been entered by the depression ofthe key was actually entered. If the key was not sufi'lciently depressedby the operator the data will not have been entered since the circuitwould not have been closed.

It had been proposed to correct this difliculty by delaying the breakingof the contact until after a short return movement of the key to itsnormal position. However, the problem then arose that in quicklystriking one key there was danger of the operator accidentallydepressing an adjacent key. The operator thus remained uncertain as towhether the data was actually entered. This uncertainty could be removedto some extent by some form of a visual indicator actuated when the keywas completely depressed or by the operator noting the values recordedon the paper strip.

It is pointed out that the switch key to which the present inventionrelates is of the type which does not remain in its depressed position,but after its release the key will quickly return to its normalposition. Thus, the keyboard does not present the operator a pattern ofdepressed keys which would quickly indicate to the operator whether ornot the data was actually entered into the calculating machine.

It is therefore the principal object of the present invention to providea novel and improved switch key assembly tor the keyboard of an electriccalculating machine.

3,430,012 Patented Feb. 25, 1969 It is another object of the presentinvention to disclose an electric switch key assembly which willindicate to the operator both acoustically and by bearing pressure onthe key that the data has been entered into the calculating machine.

It is a further object of the present invention to provide a simplifiedyet efiective arrangement for the mounting of a switch key assembly inthe keyboard of an electric calculating machine.

The present invention essentially comprises a switch key assembly havinga houosing in which there is a pair of fixed contacts. Also within thehousing is a contact element having its inner end bent over the fixedcontacts and a movable contact arm as one end mounted on the contactelement bent portion for pivotal movement. The other end of the movablecontact arm has contacts and is movable between the fixed contacts.Depression of the key actuates a key shaft which is slidably mountedwithin the housing and is operatively connected to one arm of an angularlever which is pivotally mounted within the housing. The other arm ofthe angular lever is connected by a spring to the movable contact arm.As a result of this construction, depression of the key to its lowermostor depressed position will pivot the angular lever and also snap themovable contact arm through the spring into contact with one of thefixed contacts. The key is then moved upwardly to be returned to itsnormal position under the action of a return spring. This upwardmovement of the key shaft will snap the movable contact arm back intoengagement with the second fixed contact.

The clicking noise of the movable contact between the fixed contactswill indicate to the operator that the data has been entered by thedepression of the key. In addition, the varying pressure exerted by thekey will indicate to the operator whether or not the value has beenentered.

A further aspect of the invention comprises the mounting of the switchkey housing in an opening in the keyboard by means of cooperating ribsand notches on the housing and keyboard opening respectively. Further, aresilient member is wedged between the housing and the keyboard openingto retain the housing in position and to form a tight closure in thekeyboard opening.

Other objects and advantages of the present invention will be apparentupon reference to the accompanying specification when taken inconjunction with the following drawings wherein:

FIGURE 1 is a perspective view of a portion of the keyboard showing thekeyboard openings with a switch key housing being mounted in one of saidopenings;

FIGURE 2 is an overall perspective view of the switch key housing;

FIGURE 3 is a perspective view of the resilient member utilized formounting the housing in the keyboard as illustrated in FIGURE 1;

FIGURE 4 is a longitudinal sectional view through the switch key housingas illustrated in FIGURE 2 with the parts being shown in their normal orresting positions;

FIGURE 5 is a sectional view taken along the line 55 of FIGURE 4; and

FIGURE 6 is an overall perspective view of the switch ing mechanismwithin the housing.

Proceeding next to the drawings wherein like reference symbols indicatethe same parts throughout the various views a specific embodiment of thepresent invention will be described in detail.

Referring to FIGURES 1-3 a switch key assembly according to the presentinvention is illustrated generally at 5. This assembly comprises ahousing 6 having a substantially rectangular cross section as shown. Theassembly 5 is mounted in a carrier plate 6 of the keyboard of theelectric calculating machine. The carrier plate 7 is provided with anopening into which the housing 6 is inserted.

On the upper end of the housing 6 as may be seen in FIGURES l and 2there are provided external retaining ribs 8 which engage the uppersurface of carrier plate 7 when the housing 6 is in position as shown inFIGURE 1. Spaced below retaining ribs 8 are bosses 9. The distance ofthe bosses from their respective ribs 8 is equal to the thickness of thecarrier plate 7.

The carrier plate opening 10 has a pair of notches 11 on opposed edgesthereof as shown in FIGURE 1. It may be seen one notch of each pair isagainst the edge 13 of the carrier plate opening 10 whereas the othernotches of the pair are spaced from edge 12 of the opening 10.

When the housing 6 is inserted into opening 10, the bosses 9 movethrough the corresponding notches 11 until they are positioned beneaththe carrier plate 7. The housing 6 is then moved laterally against edge12 of the opening. A resilient closure member 14 having tapered edges isthen inserted between opening edge 13 and the housing 6. The closuremember 14 has a external rib 14" which rests against the upper surfaceof carrier plates 7 when the closure member is fully inserted into theopening 10. This closure member not only retains the housing in positionwithin carrier plate opening 10 but also provides a dust-proof closurefor this opening so as to prevent the dust and other dirt frompenetrating into the mechanism beneath the keyboard of the calculatingmachine.

The cover member 14 has retaining shoulders 14' which are sprung intoposition to engage the underside of carrier plate 7, thereby securingthe closure member in position.

Proceeding next to FIGURES 4-6 the switching mechanism Within thehousing 6 will be described in detail. The switching mechanism comprisesan angular lever 15 whch is pivotally mounted on a pin 16 in the innerwall of the housing enclosure 17. The top or cover of the housingenclosure 17 is indicated at 18.

One arm 19 of the angular lever 15 has mounted on its end a tensionspring 20. The other arm of the angular lever has a cylindricalenlargement 21 thereon and is seated in a recess 22 formed in key shaft23. The key shaft 23 is mounted for vertical movement within the housingenclosure 17 and has a key 23' mounted on its upper end which projectsoutwardly of the housing. Thus, any vertical movement of key shaft 23will cause a pivoting movement of angular lever 15.

Also within the housing enclosure 17 there is provided a movable contactspring member 24 having mounted on its lower end a double faced contact25. The upper end of the contact spring member is bifurcated to form twoends 27 and 27' bent in the manner as illustrated in FIG- URES 4 and 6.The upper edges of the bifurcations 27 and 27' are indicated at 26 andare seated in recesses 28 formed in the undersides of a bent portion ofa stationary contact element 29 mounted within the housing. With thisarrangement the contact spring arm 24 is electrically connected to thecontact element 29. The tension spring is positioned between thebifurcations and has its other end connected to the contact spring arm24 as shown in FIGURES 4 and 6.

The connection of tension spring 20 to the angular lever 15 and thecontact arm 24 is such that the tension force in the rest position asillustrated in FIGURE 4 is to the left of the bearing edge 26 of themovable contact arm 24.

On depression of key 23', the key shaft 23 will move downwardly withinthe housing enclosure 17 and will pivot the angular lever 15 in theclockwise direction as viewed in FIGURE 4. As the tension force exertedby spring 20 becomes positioned to the right of the bearing surface 26,the movable contact arm 24 will snap to the right to engage a fixedcontact 30 mounted on contact element 31 which extends outwardly of thehousing enclosure.

When the operator releases his finger from key 23', a compression spring32 will return the key shaft 23 to its normal position and accordinglypivot angular lever 15 in a counter clockwise direction. As the forceexerted by spring 20 passes to the left of bearing edge 26 the contactarm 24 will be returned to its resting position as viewed in FIGURE 4with contact 25 being in engagement with fixed contact 23. Fixed contact23 is similarly mounted on contact element 31 which extends outward- 1yof the housing enclosure.

In order to minimize the possibility of the bearing edges 26 of themovable contact arm from coming out of recesses 28, the bifurcations 27and 27 may be provided with lugs which extend into recesses 34 and 35formed in the walls of the housing enclosure 17. These recesses wouldhave such a diameter so as to enable the bifurcations to pivot freelytherein but not sufficient so as to enable the bearing edges 26 tobecome removed permanently from the recesses 28.

In order to limit the range of vertical movement of key shaft 23, thekey shaft is provided with a shoulder 36 which moves in a groove formedin an inner wall of the housing enclosure and indicated at 37. Thus, thekey shaft is detained in its resting position by the shoulder 36engaging the upper end of the groove 37 as shown in FIGURE 5. Thedownward movement of the key shaft is limited by a felt pad 38positioned on the top wall 18 of the housing enclosure 17 as illustratedin FIGURES 4-6.

The contact elements 29, 31, and 31' all of which extend outwardly ofthe housing enclosure 17 are electrically connected to the circuitrywithin the calculating machine. The dead center arrangement of theangular lever, and the tension spring connecting the angular lever tothe movable contact arm assure proper making and breaking of the dataintroducing circuits upon the depression and release of the keys on thekeyboard.

Thus it can be seen that the present invention provides a switch keyassembly which gives an audible signal to the operator upon theintroduction of data into the machine when the key is depressed. Inaddition, the bearing pressure on the key resulting from the dead centerarrangement indicates to the operator whether or not the data has beenentered. The mounting of the switch key assembly in the keyboard of acalculating machine is extremely effective yet enables the switch keyassembly to be removed for maintenance or other purposes. At the sametime a dust free closure is provided between the switch key assembly andthe opening in the keyboard.

It is understood that this invention is susceptible to modifications inorder to adapt it to different usages and conditions, and accordingly,it is desired to comprehend such modifications within this invention asmay fall within the scope of the claims.

What is claimed is:

1. An electric snap switch for the key board of an electric calculatingmachine, and comprising an elongated housing having a bottom wall andnormally disposed in a vertical position, a pair of spaced fixedcontacts in said housing bottom wall, a contact element within saidhousing with its inner end being bent to extend over said fixedcontacts, there being a recess on the under-side of said bent portion, arigid movable contact arm having one end seated in said recess forpivotal movement therein and contacts on its other end movable betweensaid fixed contacts, a key shaft with a slot therein slidably mountedfor limited axial movement in said housing towards said bottom wall, afirst spring between said key shaft and housing bottom wall urging saidkey shaft outwardly of said housing to its normal unactuated position,an angular lever pivotally mounted in said housing and having first andsecond arms radially extending from the pivot point, said arms beingdirected away from the housing bottom wall, the end of said first armbeing operatively connected to said key shaft slot, and a second springconnecting said second arm of said angular lever and said movablecontact arm so that the depression of said key shaft against the forceof said first spring would move said movable contact arm against onefixed contact and return of said key shaft to its normal position willmove said movable contact arm against the other fixed contact.

2. In a switch key assembly as claimed in claim 1 wherein said bentportion of the contact element is bifurcated with recesses on theunderside of each bifurcation, the end of said movable contact armengaging said contact element being bifurcated, said first spring beingpositioned between said contact element and movable contact armbifurcations.

3. In a switch key assembly as claimed in claim 1 with there beingrecesses in the inner wall of said housing, and lugs on said movablecontact arm adjacent said pivot end seated in said housing recesses toretain said movable contact arm in engagement with said contact element.

4. In a switch key assembly as claimed in claim 1 with said key boardhaving a carrier plate with an opening therein into which said housingis positioned.

5. In a switch key assembly as claimed in claim 1 with said housinghaving a rectangular cross section, said key shaft being positionedlongitudinally of said housing, said angular lever being pivotallymounted above said contact element bent portion.

References Cited UNITED STATES PATENTS 2,779,835 1/ 1957 Russell.3,056,002 9/1962 Ball. 3,244,847 4/1966 Erpel 200172 X 3,270,157 8/ 1966Johnson.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, In, Assistant Examiner.

